Table 2.

Topiramate compared to placebo for migraine prophylaxis

Patient or population: migraine Intervention: prophylaxis with topiramate Comparison: placebo
Outcomes	№ of participants (studies) Follow-up	Certainty of the evidence (GRADE)	Relative effect (95% CI)	Anticipated absolute effects
				Risk with placebo	Risk difference with topiramate
50% or more reduction in monthly migraine days	1,959 (6 RCTs)	High	RR 1.61 (1.29 to 2.01)	275 per 1,000	168 more per 1,000 (80 more to 278 more)
Monthly migraine days	2,361 (8 RCTs)	High	-	N/A	MD 0.99 migraine days fewer (1.41 fewer to 0.58 fewer)
Adverse events leading to discontinuation	1000 (8 RCTs)	High	RD 0.08 (0.02 to 0.14)	0 per 1,000	80 more per 1,000 (20 more to 140 more)

The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI)

CI Confidence interval, MD Mean difference, RCT Randomized controlled trial, RR Risk ratio, RD Risk difference

GRADE Working Group grades of evidence

High certainty: we are very confident that the true effect lies close to that of the estimate of the effect

Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect

Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of the effect